2D framework C2N as a potential cathode for lithium–sulfur batteries: an ab initio density functional study†
One of the biggest challenges of Li–S batteries (LSBs) is the dissolution of polysulfides at the cathode side. An ideal LSB cathode should be able to prevent polysulfide (Li2Sn, 1 ≤ n ≤ 8) dissolution, and should have a strong binding energy, high capacity and a light weight, as well as being electrically conductive. Herein, we present our quantum chemical calculations combined with a genetic algorithm for a global structure search using a C2N nanosheet as a LSB cathode. The Gibbs free energies of isolated Li2Sn and LimSn_C2N (1 ≤ m, 1 ≤ n ≤ 8) are calculated to set forth the studies of both the voltages and stabilities of lithiation reactions in every step of the discharging process. Our results indicate that the polysulfides can adhere to the C2N host substrate in a thermodynamically stable cluster state without dissolution, and the system has an energy capacity of up to 1122.21 W h kg−1. The calculated band-structure shows that LimSn_C2N is metallic though the original C2N nanosheet has an optical gap of 1.96 eV. This shows that C2N could be a promising cathode material for LSBs.
- This article is part of the themed collection: 2018 Journal of Materials Chemistry A HOT Papers